Triggering on B-Jets at CDF II Amerio, S.; Casarsa, M.; Cortiana, G. ...
IEEE transactions on nuclear science,
06/2009, Letnik:
56, Številka:
3
Journal Article
Recenzirano
Odprti dostop
In this paper we present a trigger algorithm able to select online events enriched of b-jets. This feature is of central interest in order to extend the physics reach for standard model and minimal ...super symmetric model Higgs decaying into a pair of b -quarks. The algorithm fully exploits the recently upgraded CDFII tracking system and Level 2 CALorimeter cluster finder. These upgrades are necessary to cope with Tevatron increasing luminosity and provide new and refined trigger primitives that are the key elements of our algorithm together with the already existing silicon vertex trigger. A b -hadron can travel some millimeters before decaying and the trigger algorithm exploits this characteristic by searching for tracks displaced with respect to the primary vertex and matched to energetic jets of particles. We discuss the study and the optimization of the algorithm, its technical implementation as well as its performance. The new trigger provides an efficient selection for Higgs decaying into a pair of b -quarks and runs up to high luminosity with an acceptable occupancy of the available bandwidth.
A high-granularity timing detector for the ATLAS phase-II upgrade Casado, M.P.; Adam Bourdarios, C.; Belfkir, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2022, Letnik:
1032
Journal Article
Recenzirano
Odprti dostop
The large increase of pileup interactions is one of the main experimental challenges for the HL-LHC physics programme. A powerful new way to mitigate the effects of pileup is to use high-precision ...timing information to distinguish between collisions occurring close in space but well-separated in time. A High-Granularity Timing Detector, based on low gain avalanche detector technology, is therefore proposed for the ATLAS Phase-II upgrade. Covering the pseudorapidity region between 2.4 and 4.0, this device will improve the detector physics performance in the forward region. The typical number of hits per track in the detector was optimized so that the target average time resolution per track for a minimum-ionising particle is 30 ps at the start of lifetime, increasing to 50 ps at the end of HL-LHC operation. The high-precision timing information improves the pileup reduction to improve the forward object reconstruction, complementing the capabilities of the upgraded Inner Tracker (ITk) in the forward regions of ATLAS and leading to an improved performance for both jet and lepton reconstruction. These improvements in object reconstruction performance translate into sensitivity gains and enhance the reach of the ATLAS physics programme at the HL-LHC. In addition, the HGTD offers unique capabilities for the online and offline luminosity determination, an important requirement for precision physics measurements.
Impedance spectroscopy was used to confirm the presence of a poorly conductive sulphur layer on a platinum electrode during the electrolysis of HS
−. The double layer capacitance was found to be ...close to 40μF cm
−2 at open circuit potential. When electrolysis commenced the double layer capacitance was greatly reduced (< 5μF cm
−2). The charge transfer resistance increased to few hundred ohms cm
2 during electrolysis. Double potential chronocoulometric experiments were also performed. The chronocoulometric analysis showed that the average stoichiometry of the intermediate polysulphide ions in the electrolysis reaction was S
2.5
2− in the anodic step and S
4.3
2− in the cathodic step.
A stable solid state H
2S—O
2 fuel cell has been developed and operated at 1 atm and 20–90°C. A series of anode catalysts has been examined using Nafion
® as a common proton conducting membrane; ...those containing Pd and Pt were found to be effective using H
2 or H
2S as the anode feed gas, but MoS
2—C catalysts were effective for use of H
2S but not for H
2. The highest potential attained using H
2S and
Pd/
C catalyst was 722 mV (theory: 1140 mV). When H
2S was used as anode feed the potential decreased up to 35% over 24 h as sulfur was deposited on the anode. The efficiency of the cell increased with temperature up to 90°C.
Calibration results of CMS electromagnetic calorimeter photodetectors Balandras, A.; Depasse, P.; Donini, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2003, Letnik:
504, Številka:
1-3
Journal Article
Recenzirano
The Compact Muon Solenoid is one of two generic detectors currently being constructed for the Large Hadron Collider at CERN foreseen to begin data taking in 2007. The electromagnetic calorimeter ...consists of a barrel and endcaps made of PbWO4 scintillating crystals. In the barrel, the scintillation signal is read out by Hamamatsu avalanche photodiodes, connected in parallel in a structure called a “capsule”, one for each of the 61200 channels. We present the calibration results and performance statistics obtained for more than 5000 production capsules.
A measurement of the $ZZ$ production in the $\ell^{-}\ell^{+}\ell^{\prime -}\ell^{\prime +}$ and $\ell^{-}\ell^{+}\nu\bar{\nu}$ channels $(\ell = e, \mu)$ in proton--proton collisions at $\sqrt{s} = ...8$ TeV at the Large Hadron Collider at CERN, using data corresponding to an integrated luminosity of 20.3 fb$^{-1}$ collected by the ATLAS experiment in 2012 is presented. The fiducial cross sections for $ZZ\to\ell^{-}\ell^{+}\ell^{\prime -}\ell^{\prime +}$ and $ZZ\to \ell^{-}\ell^{+}\nu\bar{\nu}$ are measured in selected phase-space regions. The total cross section for $ZZ$ events produced with both $Z$ bosons in the mass range 66 to 116 GeV is measured from the combination of the two channels to be $7.3\pm0.4\textrm{(stat)}\pm0.3\textrm{(syst)}\pm0.2\textrm{(lumi)}$ pb, which is consistent with the Standard Model prediction of $6.6^{+0.7}_{-0.6}$ pb. The differential cross sections in bins of various kinematic variables are presented. The differential event yield as a function of the transverse momentum of the leading $Z$ boson is used to set limits on anomalous neutral triple gauge boson couplings in $ZZ$ production.
The top quark mass is measured in the $t\bar{t}\to$ dilepton channel (lepton $= e, \mu$) using ATLAS data recorded in the year 2012 at the LHC. The data were taken at a proton--proton centre-of-mass ...energy of $\sqrt{s}=$ 8 TeV and correspond to an integrated luminosity of about 20.2 fb$^{-1}$. Exploiting the template method, and using the distribution of invariant masses of lepton--b-jet pairs, the top quark mass is measured to be $m_{top} =$ 172.99 $\pm$ 0.41 (stat) $\pm$ 0.74 (syst) GeV, with a total uncertainty of 0.84 GeV. Finally, a combination with previous ATLAS $m_{top}$ measurements from $\sqrt{s}=$7 TeV data in the $t\bar{t}\to$ dilepton and $t\bar{t}\to$ lepton+jets channels results in $m_{top} =$ 172.84 $\pm$ 0.34 (stat) $\pm$ 0.61 (syst) GeV, with a total uncertainty of 0.70 GeV.
Two searches for new phenomena in final states containing a same-flavour opposite-lepton (electron or muon) pair, jets, and large missing transverse momentum are presented. These searches make use of ...proton--proton collision data, collected during 2015 and 2016 at a centre-of-mass energy $\sqrt{s}=13$ TeV by the ATLAS detector at the Large Hadron Collider, which correspond to an integrated luminosity of 14.7 fb$^{-1}$. Both searches target the pair production of supersymmetric particles, squarks or gluinos, which decay to final states containing a same-flavour opposite-sign lepton pair via one of two mechanisms: a leptonically decaying Z boson in the final state, leading to a peak in the dilepton invariant-mass distribution around the Z boson mass; and decays of neutralinos (e.g. $\tilde{\chi}_2^0 \rightarrow \ell^+\ell^- \tilde{\chi}_1^0$), yielding a kinematic endpoint in the dilepton invariant-mass spectrum. The data are found to be consistent with the Standard Model expectation. Results are interpreted in simplified models of gluino-pair (squark-pair) production, and provide sensitivity to gluinos (squarks) with masses as large as 1.70 TeV (980 GeV).
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